1. Field of the Invention
The invention relates to an improved anti-friction sucker rod coupling and guide.
2. Brief Description of the Prior Art
A method widely used for producing oil from subterranean formations is the reciprocation of a bottom hole pump by a long string of sucker rods actuated in a production tubing. A pumping unit powered by a prime mover such as an electric motor or a gas engine is positioned at the surface of the well and transmits reciprocal motion through the sucker rods to the pump. The total length of the sucker rods commonly varies from a few hundred feet to more than 15,000 feet.
Because of intentional deviation from vertical in drilling, or for a variety of unintentional causes, many oil wells have crooked holes so that on the up and down strokes of the sucker rod, the sucker rod, and particularly the sucker rod couplings are caused to rub against the well tubing. Even in wells which are straight, a pumping rate sometimes is used such that on the down stroke a portion of the sucker rods are forced under compression causing them to buckle slightly and causing rubbing against the side of the tubing which in turn results in expensive wear to the well tubing and/or the sucker rod string and consequent down time required to replace sucker rod worn by such rubbing.
Perhaps of even greater importance in these times of rapidly rising energy costs and scarcity of fuel is the increased amount of energy required to overcome the frictional loss caused by such rubbing.
For these reasons, particularly in order to conserve energy and reduce costs, it is highly desirable to provide a coupling which will have a reduced friction drag against the tubing, which will not wear holes in the tubing, and which will not wear away the coupling itself.
Attempts have been made to provide sucker rod couplings having improved resistance to wear. One method of attempting to counteract the wear of the coupling includes case hardening the coupling itself to provide an exterior surface of extremely hard steel calculated to resist wear. This is a satisfactory procedure to lessen wear on the coupling itself, but does not assist at all in eliminating the wearing away of the tubing in which the sucker rods operate nor in reducing the overall frictional loss of energy required for pumping.
Various other attempts have been made to overcome the problems heretofore mentioned with varying amounts of success. The closest approach to my invention appears to be exemplified by U.S. Pat. No. 3,528,499 wherein a plastic-fluted rod guide is fastened about a sucker rod, the rod guide being adopted to slide on the sucker rod rather than on the tubing string. However, the sucker rod is not polished nor does it have an anti-friction surface, and the sucker rod has tapered ends which would tend to deform the rod guide. It lacks the energy conserving anti-friction relationship between the anti-friction rod member surface and the mated rod guide anti-friction surface which is an important aspect of my invention.
U.S. Pat. Nos. 2,200,758 and 2,001,270 represent another approach to the problem and disclose rod guides which frictionally engage the tubing by means of spring members and the like and which are adapted to slideably fit about sucker rod joints. Again, the anti-friction relationship improvement of my invention is not suggested.
U.S. Pat. Nos. 3,049,382, 3,490,526, and 3,414,337 are exemplary of another approach which is in commercial use. According to this approach the rod guide moves with the sucker rod string and slides within the tubing. Again, my invention constitutes an improvement and demonstrates substantial energy savings over this type of system.
In a related art, U.S. Pat. Nos. 2,072,320, 2,572,307, and 3,894,780 disclose drilling string guides wherein a drilling string having rotary motion is centralized.
My invention constitutes a substantial advance in the art, as exemplified above, by providing for a very substantial reduction in the energy required to pump oil wherein a sucker rod string is employed, particularly from crooked bore holes.